The European Union sought Monday to ease concerns that citizens might be obliged to get shots against the coronavirus before they’re allowed to travel, as debate swirls over the use of vaccination certificates to help reopen tourism across the 27-nation bloc.

The European Commission has been weighing a Greek proposal to issue vaccination certificates to help get travellers to their vacation destinations more quickly and avoid another disastrous summer for Europe’s tourism sector.

Greece plans to issue digital vaccination certificates to each person inoculated against COVID-19. EU heads of state and government are due to discuss the proposal at a video-summit on Thursday.

European Commission Vice-President Maros Sefcovic insisted that “vaccination is voluntary.” He noted that some people cannot be inoculated for health reasons while others might simply object.

“We are taking all the precautions that we would not create any ground for different treatment of these people, or any kind of limitations of their rights,” he told reporters after taking part in videoconference talks between European affairs ministers.

Sefcovic said the priority now must be to gather data about the disease and its treatment on digital platforms on a Europe-wide scale so that health experts can compare the way the virus mutates, how the vaccines are working and whether testing standards are harmonized across the 27 member countries.

“We need to make sure that the data would be collected electronically in respect of all data privacy rules and it should be done on interoperable platforms so we can share the data,” he said, adding that it’s need to assess the “efficiency of the vaccines, for the evaluation of the whole vaccination process.”

Vaccinations have started across the 27-nation EU, but it is unclear what proportion of the population will be vaccinated in time for the summer holiday season.